Abstract:

An optical pickup and an optical information recording and reproducing
device in which spherical aberration correction control after a disc is
loaded can be efficiently made in a short time. Before an information
recording medium is loaded into a drive, an optical axis direction
position of a concave lens is preset to a state so as to optimize a
converging spot on a recording surface of a single-layered medium of as a
first recording medium or a predetermined layer (first layer having a
substrate thickness of 0.1 mm) of a medium having two or more layers to
which the recording/reproduction is executed by a laser light source.
After the information recording medium is loaded, if it is determined to
be a second (third) recording medium to which the recording/reproduction
is executed by a laser light source, setting of the optical axis
direction position of the concave lens is changed.

Claims:

1-13. (canceled)

14. An optical pickup for recording/reproducing information by irradiating
a light spot onto an information recording medium, comprising:a first
laser light source, for emitting light having a wavelength λ1;a
second laser light source for emitting light having a wavelength λ2
which is larger than the wavelength λ1 of light emitted from the
first laser light source;a spherical aberration correcting optical
element which is arranged on an optical path of the light emitted from
the first laser light source and can move in an optical axis direction;a
position detecting sensor, for detecting the position of the spherical
aberration correcting optical element;a first objective lens, which can
converge the light emitted from the first laser light source so that the
light converged by the first objective lens reaches a first information
recording medium, having two recording layers of L0 and L1;a second
objective lens, which can converge the light emitted from the second
laser light source so that the light converged by the second objective
lens reaches a second information recording medium; anda photodetector,
for detecting the reflected light from an information recording medium;
wherein:the initial position of the spherical aberration correcting
optical element is set so as to optimize a converging spot near an
intermediate position between the recording layer L0 and L1 of the first
information recording medium: andthe spherical aberration correcting
optical element moves to the initial position on the basis of a signal
from the position detecting sensor when an initial operation is
performed.

15. An optical pickup according to claim 14, wherein the state of
optimizing a converging spot is that a total wave aberration is around
minimum or a converging spot length is around minimum.

16. An optical pickup according to claim 14, wherein the first objective
lens is set so as to optimize the converging spot near an intermediate
position between the recording layer L0 and L1 of the first information
recording medium when parallel light, having wavelengths λ1,
enters.

17. An optical pickup according to claim 14, wherein the position of the
spherical aberration correcting optical element is set so as to allow
divergent light to enter the first objective lens when the optical pickup
reads or writes data on the recording layer L0 of the first information
recording medium.

18. An optical pickup according to claim 14, wherein the position of the
spherical aberration correcting optical element is set so as to allow
converging light to enter the first objective lens when the optical
pickup reads or writes data on the recording layer L1 of the first
information recording medium.

19. An optical pickup according to claim 14, wherein the position of the
spherical aberration correcting optical element is finely set on the
basis of a signal from the photodetector so as to allow divergent light,
having wavelength λ1, or converging light, having wavelength
λ1, to enter the first objective lens.

20. An optical pickup according to claim 14, wherein;the spherical
aberration correcting optical element moves so as to optimize a
converging spot at the position, which is around 0.1 mm from a surface of
protecting layer of the first information recording medium, when the
optical pickup reads or writes data on the recording layer L0 of the
first information recording medium; andthe spherical aberration
correcting optical element moves so as to optimize a converging spot at
the position, which is around 0.075 mm from the surface of the protecting
layer of the first information recording medium, when the optical pickup
reads or writes data on the recording layer L1 of the first information
recording medium.

21. An optical pickup according to claim 14, comprising:a third laser
light source, emitting light having a wavelength λ3, wherein:the
second object lens can converge the light, having wavelength λ2, so
that the light, having wavelengths λ2, reaches a recording layer of
a DVD, andthe second object lens can converge the light, having
wavelength λ3, so that the light having wavelengths λ3,
reaches a recording layer of a CD.

22. An optical pickup according to claim 14, wherein the first objective
lens and the second objective lens are arranged with a tangential
direction or a radial direction of the information recording medium.

Description:

INCORPORATION BY REFERENCE

[0001]The present application claims priority from Japanese application
JP2005-052245 filed on Feb. 28, 2005, the content of which is hereby
incorporated by reference into this application.

BACKGROUND OF THE INVENTION

[0002]The invention relates to an optical pickup for reproducing or
recording information by irradiating a laser beam onto a disk-shaped
information medium.

[0003]A high density optical disk device using a blue-violet laser having
a laser wavelength of a band of 405 nm, an objective lens having a
numerical aperture of 0.85, and a BD (Blu-ray Disc) having a substrate
thickness of 0.1 mm has been realized as a product. At present, a medium
of a single-layered disc and a medium of a double-layered disc exist as
BDs. According to the BD standard, in the double-layered disc, there is a
difference of the substrate thickness of 25 μm between the first
recording layer and the second recording layer. Further, in each
recording layer of the double-layered disc or in the single-layered disc,
the substrate thickness varies every disc and even in a single disc, the
substrate thickness varies in dependence on a recording or reproducing
position (in the BD standard, a variation of up to ±5 μm is
permitted). If there is such a variation or difference of the substrate
thickness as mentioned above, a spherical aberration occurs in a light
spot on the disc recording surface and it is difficult to record and
reproduce. To correct such a spherical aberration, the optical pickup is
equipped with an optical element for spherical aberration correction such
as a beam expander. A typical constructional example of such an element
has been disclosed in, for example, a Patent Document 1 (JP-A-2002-304763
(pages 21-23, FIGS. 1, 4, and 6)).

[0004]As a technique regarding the spherical aberration correction, for
example, a technique in which a predetermined correction value of a
spherical aberration correcting system is preliminarily stored in a ROM
provided for the optical pickup and, upon recording and reproducing of
the BD, the correcting system is driven on the basis of the correction
value read out of the ROM has been disclosed in, for example, a Patent
Document 2 (JP-A-2003-257069 (pages 1-7, FIGS. 1, 2, and 3)).

SUMMARY OF THE INVENTION

[0005]In the optical disk device corresponding to the BD mentioned above,
until the disc is loaded, information showing to which one of the
single-layered disc and the double-layered disc such a disc corresponds
or, even if the disc is the single-layered disc, information indicative
of a degree of variation of the substrate thickness cannot be detected on
the optical pickup side. When the disc is loaded into the device from
such a state, in the optical pickup, there is executed aberration
correction control in which a spherical aberration amount due to the
substrate thickness error is detected, the optical element for the
spherical aberration correction is driven in an optical axis direction
from a certain initial position (not determined yet) and moved to a
proper position, and the spherical aberration is reduced up to a level at
which no trouble is caused in the recording and reproduction. However, in
such correction control, there is the following problem: an initial
setting position of the optical element for the spherical aberration
correction is not preset and it takes time until the proper position of
the optical element is searched for, or the aberration correction control
fails and the recording and reproduction of the disc cannot be started.
Under the condition that the use frequency of the single-layered disc and
the first layer of the double-layered disc of the BDs is considered to be
highest, solving the above problem is indispensable in order to improve
use efficiency of a drive. In consideration of the above problem, it is
an object of the invention to provide an optical information recording
and reproducing device or an optical information recording device having
high use efficiency.

[0006]The above object is accomplished by the inventions disclosed in
Claims.

[0007]According to the invention, the optical information recording and
reproducing device or optical information reproducing device having high
use efficiency can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]These and other features, objects and advantages of the present
invention will become more apparent from the following description when
taken in conjunction with the accompanying drawings wherein:

[0009]FIG. 1 is a diagram showing a construction of an optical pickup in
the embodiment 1;

[0010]FIGS. 2A to 2C are diagrams for explaining an objective lens 113 in
the embodiment 1;

[0011]FIGS. 3A and 3B are a diagram and a graph showing an example of a
relation between a divergence angle of incident light to the objective
lens 113 in the case of a BD medium and a wave front aberration of a
converging spot 302 in the embodiment 1;

[0012]FIG. 4 is a diagram for explaining a layout and shape parameters of
a beam expander element 110 in the embodiment 1;

[0013]FIG. 5 is a graph showing a relation between a substrate thickness
of the BD medium and an interval between a concave lens 108 and a convex
lens 109 which are necessary in the embodiment 1;

[0014]FIG. 6 is a graph showing an aberration correcting effect by the
beam expander shown in Table 1;

[0015]FIG. 7 is a diagram for explaining detecting surfaces of a
photodetector 118 and an error signal in the embodiment 1;

[0016]FIG. 8 is a diagram showing an example of a construction of a
peripheral portion of the beam expander element 110 in the embodiment 1;

[0017]FIG. 9 is a flowchart showing an example of an assembling adjusting
flow of a BD optical system in the embodiment 1;

[0018]FIG. 10 is a flowchart showing an example of a drive operating flow
in the case of the BD medium in the embodiment 1;

[0019]FIGS. 11A and 11B are graphs showing a focusing error signal in the
embodiment 1;

[0020]FIGS. 12A and 12B are graphs showing a focusing error signal in the
embodiment 1;

[0021]FIG. 13 is a flowchart for explaining an operating flow in the case
where a focal point is moved from an L0 layer to an L1 layer of the BD
medium in the embodiment 1;

[0022]FIG. 14 is a flowchart showing an example of an assembling adjusting
flow in a DVD optical system and a CD optical system in the embodiment 1;

[0023]FIG. 15 is a flowchart showing an example of a drive operating flow
in the case of a DVD medium and a CD medium in the embodiment 1;

[0024]FIG. 16 is a diagram showing the first example in the embodiment 2;

[0026]FIG. 18 is a diagram showing the second example in the embodiment 2;

[0027]FIG. 19 is a diagram showing the third example in the embodiment 2;
and

[0028]FIG. 20 is a diagram showing the fourth example in the embodiment 2.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029]Although the following embodiments are considered as best modes for
carrying out the invention, the invention is not limited to the following
embodiments so long as the object of the invention is accomplished.

[0030]The embodiment 1 will be described hereinbelow. FIG. 1 shows a
construction of an optical pickup in the embodiment. It is the optical
pickup which can cope with each medium of the BD, DVD, and CD and uses a
common objective lens. Light emitted from a blue-violet laser 101 having
a wavelength of a band of 405 nm passes through a beam shaping element
102 and a half wave plate 103, is branched into a main beam and two sub
beams by a diffraction grating 104 for the BD, and passes through a
polarization beam splitter 105. Parallel light is irradiated from a
collimator lens 106 for the BD. The parallel light is reflected by a half
mirror 107 and passes through a concave lens 108 and a convex lens 109,
its beam diameter is enlarged, and the resultant light is reflected by a
rising mirror 111. After that, the light is transmitted through a quarter
wave plate 112 and an aperture restricting element 131 for the CD, is
converged by an objective lens 113, and reaches an information recording
surface of an information recording medium 114 (in this case, a BD medium
having one, two, or more recording layers). The objective lens 113 and
the aperture restricting element 131 for the CD mounted in a common
holder (not shown) and parallel movement in the surface oscillating
direction and the radial direction of the information recording medium
114 and rotational movement in which the tangential direction of the
information recording medium 114 is set to an axis can be executed by an
actuator 134. To compensate a spherical aberration which is caused in
association with a substrate thickness error of the information recording
medium 114, a beam expander element 110 is constructed by a pair of the
concave lens 108 and the convex lens 109 and can be moved in the optical
axis direction shown by arrows 132 and 133 by an actuator 135. The
reflection return light from the information recording medium 114 is
transmitted through the objective lens 113 and the quarter wave plate
112, reflected by the rising mirror 111, transmitted through the convex
lens 109 and concave lens 108, and reflected by the half mirror 107.
After that, the light is transmitted through the collimator lens 106, is
reflected by the polarization beam splitter 105, is converged by a
detecting lens 117, and reaches a detecting surface of a photodetector
118 for the BD. An RF signal and servo signals (focusing error signal,
DPP signal, and the like) are detected by the photodetector 118 for the
BD and a spherical aberration error signal is formed on the basis of
those signals and detected. A part of the parallel light emitted from the
collimator lens 106 for the BD is transmitted through the half mirror
107, is converged by a lens 115, reaches a front monitor 116 for the BD,
and a light emission amount of the blue-violet laser 101 is monitored.

[0031]Light emitted from a red laser 119 having a laser wavelength of a
band of 660 nm is transmitted through an auxiliary collimator lens 120,
is branched into a main beam and two sub beams by a diffraction grating
121 for the DVD, and passes through a synthetic prism 122, and
thereafter, is reflected by a half mirror 123. Parallel light is
irradiated from a collimator lens 124, is transmitted through the half
mirror 107, passes through the concave lens 108 and the convex lens 109,
its beam diameter is enlarged, and after that, the resultant light is
reflected by the rising mirror 111, transmitted through the quarter wave
plate 112, converged by the objective lens 113, and reaches the
information recording surface of the information recording medium 114 (in
this case, the DVD medium having one or two recording layers). The
reflection return light from the information recording medium 114 is
transmitted through the objective lens 113 and the quarter wave plate
112, reflected by the rising mirror 111, transmitted through the convex
lens 109 and concave lens 108, and transmitted through the half mirror
107. After that, the light is converged by the collimator lens 124 and a
detecting lens 127, and reaches a detecting surface of a photodetector
128 for the DVD/CD. An RF signal and servo signals (focusing error
signal, DPP signal, and the like) are detected by the photodetector 128
for the DVD/CD. A part of the light transmitted through the synthetic
prism 122 is transmitted through the half mirror 123, is converged by a
lens 125, reaches a front monitor 126 for the DVD/CD, and a light
emission amount of the red laser 119 is monitored.

[0032]Light emitted from an infrared laser 129 having a laser wavelength
of a band of 780 nm is branched into a main beam and two sub beams by a
diffraction grating 130 for the CD and is reflected by the synthetic
prism 122 and the half mirror 123. The parallel light is irradiated from
the collimator lens 124, is transmitted through the half mirror 107, and
enters the concave lens 108. The concave lens 108 is moved in the
direction shown by the arrow 132. Divergent light is emitted from the
convex lens 109. After that, the light is reflected by the rising mirror
111, transmitted through the quarter wave plate 112 and the aperture
restricting element 131 for the CD, converged by the objective lens 113,
and reaches the information recording surface of the information
recording medium 114 (in this case, the CD medium). Since an optical path
until the reflection return light from the information recording medium
114 reaches the information recording surface of the photodetector 128
for the DVD/CD is the same as that of the DVD system as mentioned above,
its explanation is omitted here. Although the red laser 119 and the
infrared laser 129 are separately provided in FIG. 1, a laser of two
wavelengths in which those lasers are integrated can be also used in
order to simplify the optical system. In dependence on the specifications
of the drive, for example, it is possible to use an optical system in
which the blue-violet laser 101 and the red laser 119 are mounted without
using the infrared laser 129.

[0033]The objective lens 113 will now be described with reference to FIGS.
2A to 2C. FIG. 2A shows the state where the light is converged in a BD
double-layers medium 201. Parallel light 202 having the wavelength of the
band of 405 nm passes through the aperture restricting element 131 for
the CD as it is and is converged by the operation of a refracting plane
203. The objective lens 113 is designed so that a wave front aberration
of a converging spot 206 is optimized at a substrate thickness t1 (32
0.0875 mm) in an intermediate layer 205 (shown in a broken line portion)
comprising an L0 layer having a substrate thickness of 0.1 mm and an L1
layer having a substrate thickness of 0.075 mm. The objective lens 113 is
designed so that grating grooves 204 formed concentrically on the
refracting plane 203 do not have a diffraction function in such a manner
that a numerical aperture of the refracting plane 203 is equal to 0.85
for the light having the wavelength of the band of 405 nm. FIG. 2B shows
the state where the light is converged in a DVD medium 207. Parallel
light 208 having the wavelength of the band of 660 nm passes through the
aperture restricting element 131 for the CD as it is, is diffracted by
the grating grooves 204, and is converged by the refracting plane 203.
The objective lens 113 is designed so that an aberration of a converging
spot 209 is optimized at a substrate thickness t2 (32 0.6 mm). The
objective lens 113 is designed so that grating grooves 204 are formed in
a beam diameter range where the numerical aperture is equal to 0.65 for
the light having the wavelength of the band of 660 nm in such a manner
that the spherical aberration which is caused due to the wavelength
difference of about 255 nm and the substrate thickness difference of
about 0.5 mm from those in the case of the BD of FIG. 2A is set off. FIG.
2C shows the state where the light is converged in a CD medium 210. As
for divergent light 211 having the wavelength of the band of 780 nm, a
beam diameter of the light entering the objective lens 113 is restricted
by the aperture restricting element 131 for the CD and the numerical
aperture of the objective lens 113 lies within a range from 0.45 to 0.5.
The objective lens 113 is designed so that the light is diffracted by the
grating grooves 204, converged by the refracting plane 203, and the
aberration of the converging spot 212 is optimized at a substrate
thickness t3 (=1.2 mm).

[0034]As described in FIG. 2A, in the case of the BD medium, the objective
lens 113 is designed so that the wave front aberration of the converging
spot 206 is optimized at the substrate thickness t1 (32 0.0875 mm).
However, it is sufficiently considered that there are two kinds of BD
media such as single-layered medium and double-layered medium and both of
them are used at present and that at a point when the
recording/reproduction of the double-layered medium is started, the use
frequency of the LO layer of the first layer is highest. Therefore, it is
necessary to set in such a manner that the wave front aberration of the
converging spot becomes minimum at a reference value (32 0.1 mm) of the
substrate thickness of the single-layered medium and the substrate
thickness of the L0 layer of the double-layered medium. For this purpose,
as shown in FIG. 3A, it is necessary to allow predetermined divergent
light 301 to enter the objective lens 113. FIG. 3B shows an example of
calculations executed to find which kind of divergent light should be
made to enter in order to minimize a converging spot 302 at the substrate
thickness of 0.1 mm. The wavelength is set to 405 nm, the numerical
aperture of the objective lens 113 is set to 0.85, the refractive index
of the substrate is set to 1.62, a distance L between an incident plane
303 of the objective lens 113 and a virtual light source 304 of the
divergent light 301 is changed, and the wave front aberration of the
converging spot 302 is calculated. An axis of abscissa indicates a
divergence angle θ (°) of the incident light entering the
objective lens 113 converted from the distance L. An axis of ordinate
indicates a wave front aberration value (λrms) of the converging
spot 302. A calculation result is as shown by a curve 305. It will be
understood from the result that by setting the divergence angle θ
of the incident light to θ=0.16°, the wave front aberration
value of the converging spot at the substrate thickness of 0.1 mm can be
minimized and this value is suppressed to an enough small value of 0.0027
λrms.

[0035]Specific examples of the beam expander element 110 designed on the
basis of the result of FIG. 3B will be described hereinbelow. FIG. 4
shows a layout and shape parameters of the concave lens 108 and the
convex lens 109 of the beam expander element 110. In this example, in the
case of an initial interval B between the concave lens 108 and the convex
lens 109, parallel light 401 entering the concave lens 108 is magnified
and emitted as parallel light 402 from the convex lens 109. In this
example, the convex lens 109 is fixed and when the concave lens 108 is
moved in parallel in the optical axis direction from the initial interval
B, the divergent light or converging light is emitted from the convex
lens 109 and enters the objective lens 113.

[0036]Design values are as shown in Table 1. The initial interval B=2 mm
and a distance C between the convex lens 109 and the incident plane of
the objective lens is set to (C=15.7 mm). FIG. 5 shows an example of
calculations of the interval between the concave lens 108 and the convex
lens 109 which are necessary to minimize the wave front aberration of the
converging spot when the substrate thickness of the BD medium fluctuates.
A straight line 501 shows the calculation result. It will be understood
that it is sufficient to set the interval to 1.755 mm, for example, at
the substrate thickness of 0.1 mm in the L0 layer.

[0037]It will be understood that it is sufficient to set the interval to
2.25 mm, for example, at the substrate thickness of 0.075 mm in the L1
layer. Further, the correctable substrate thickness error converted by
the movement amount of 1 mm of the concave lens 108 is equal to 0.05 mm.
FIG. 6 shows an example of calculations of the substrate thickness of the
BD medium and the wave front aberration of the converging spot. A curve
601 shows the case where the aberration correction by the beam expander
element 110 is not made. When the substrate thickness is deviated from
the design reference value of 0.0875 mm, the wave front aberration of the
converging spot deteriorates suddenly. On the other hand, in the case
where the aberration correction by the beam expander element 110 is made,
the result is as shown by a curve 602. It will be understood that even if
the substrate thickness fluctuates by ±0.025 mm from the design
reference value of 0.0875 mm, the wave front aberration of the converging
spot is suppressed to an enough small value of 0.005 λrms or less.

[0038]As shown in FIG. 7, in the photodetector 118 for the BD, as
photodetecting surfaces, a main detecting surface 701 is formed in the
center portion, sub detecting surfaces 702 and 703 are formed in the
upper and lower portions, and the photodetector 118 has eight detecting
surfaces A to D and E to H. Main light 704 in which the return light from
the information recording medium 114 of 0-order light branched by the
diffraction grating 104 for the BD has been converged by the detecting
lens 117 enters the eight detecting surfaces A to D. Primary light 705
branched by the diffraction grating 104 for the BD enters the eight
detecting surfaces E and F. Sub light 706 in which the return light from
the information recording medium 114 of--primary light branched has been
converged by the detecting lens 117 enters the eight detecting surfaces G
and H. An astigmatism method is used for detection of a focusing error.
The error signal is obtained by an arithmetic operation of [A+C-(B+D)]
and the RF signal is obtained by an arithmetic operation of [A+B+C+D].

[0039]FIG. 8 shows an example of a construction of a peripheral portion of
the beam expander element 110. The convex lens 109 is fixed to a frame
(not shown) and the concave lens 108 is attached to a holder 801 and
supported by guide shafts 802 provided on the right and left sides. The
holder 801 is connected to a lead screw 804 of a stepping motor 803 and
is moved in parallel in the optical axis direction 132 or 133 by the
rotational motion of the lead screw 804. A position detecting sensor 805
to detect the position in the optical axis direction of the holder 801
including the concave lens 108 is attached to the frame (not shown) so as
to face the holder 801. Reference numeral 806 denotes a reflecting
surface provided for the holder 801. The position detecting sensor 805 is
designed so as to have characteristics in which an output voltage
linearly changes in accordance with a distance between the position
detecting sensor 805 and the reflecting surface 806. Although a
contactless reflecting type sensor is used as a position detecting sensor
805 in FIG. 8, it is also possible to use another type such as
contactless transmitting type, contact type using a potentiometer, or the
like.

[0040]In the embodiment, when the optical pickup is assembled, adjustment
is made, for example, in steps 901 to 908 shown in FIG. 9. First, a first
reference disc accurately manufactured so that the substrate thickness is
set to the same value of 0.1 mm as that of the L0 layer is used, an
interferometer, a spot observing apparatus, or the like is used, the
stepping motor 803 is driven so that the converging spot obtained by the
objective lens 113 enters the optimum state, and the initial position of
the concave lens 108 is adjusted. Or, the optical pickup is set into the
state where the focusing servo can be performed, the stepping motor 803
is driven so as to maximize an amplitude of the RF signal or optimize a
jitter value and an error rate value, and the initial position of the
concave lens 108 is adjusted. In this state, electrical adjustment is
made on a circuit 807 side of the position detecting sensor 805 so that a
first predetermined voltage V1 is outputted from the circuit 807 (for
example, the predetermined voltage V1 is recorded into the circuit 807 or
the like). Subsequently, a second reference disc accurately manufactured
so that the substrate thickness is set to the same value of 0.075 mm as
that of the L1 layer is used and the position of the concave lens 108 is
adjusted so that the converging spot by the objective lens 113 is set
into the optimum state or a jitter value and the error rate value are
optimized. After that, electrical adjustment is made on the circuit 807
side so that a second predetermined voltage V2 is outputted from the
circuit 807 (for example, the predetermined voltage V2 is recorded into
the circuit 807 or the like).

[0041]The operation of the drive of the optical pickup adjusted as
mentioned above is, for example, as shown in steps 1001 to 1010 in FIG.
10 and will be explained hereinbelow also with reference to FIG. 8. When
a power source of the drive is turned on, a drive controller 809 refers
to the circuit 807 of the position detecting sensor 805 and a driver
circuit 808 of the stepping motor 803. The stepping motor 803 is driven
while observing the output voltage from the circuit 807. When the voltage
V1 is outputted, the stepping motor 803 is stopped. In this state, the
blue-violet laser 101 is turned on and a focusing acquisition is
performed to the L0 layer. When the initial position in the optical axis
direction of the concave lens 108 is the optimum position, a good
S-character curve 1101 is obtained as shown in FIG. 11A. However, when
the initial position in the optical axis direction of the concave lens
108 is deviated from the optimum position, the spherical aberration
occurs in the light spot on the disc and the light spot cannot be
converged. Thus, the focusing error signal deteriorates as shown by as
S-character curve 1102 or 1103 in FIG. 11B (the amplitude is decreased
and an offset occurs) and there is a risk of failure in the focusing
acquisition. To avoid such a situation, the initial position of the
concave lens 108 is forcedly determined so that the first predetermined
voltage V1 is outputted from the circuit 807 of the position detecting
sensor 805 (as described above) before the focusing acquisition is
performed to the L0 layer. By this method, the good S-character curve is
obtained as shown in FIG. 11A and the focusing acquisition operation can
be stably started. Further, actually, since the substrate thickness of
the L0 layer has a variation depending on a radial direction position of
the disc, there is a possibility of fluctuation of the optimum position
of the concave lens 108. For example, while the focusing control is made,
the position of the concave lens 108 is finely adjusted so that the
amplitude of the RF signal obtained by photodetector 118 for the BD is
maximized or the jitter and error rate value are optimized. Such fine
adjustment is made, for example, when radial direction position of the
disc of the optical pickup is changed. Since information regarding the
optimum position of the concave lens 108 is obtained by the driving
operation so far, it is stored into the drive controller 809 together
with an operation history. When the disc is ejected from the drive and
the power source is again turned on from the off state of the power
source of the drive, or when the power source is again turned on from the
off state of the power source of the drive while the disc is inserted in
the drive, the obtained information is immediately transferred to the
circuit 807 and the driver circuit 808 from the drive controller 809. By
constructing the system as mentioned above, such an effect that the
stable driving operation can be executed in a short time and the use
efficiency is improved can be obtained.

[0042]The case of subsequently moving the focal point to the L1 layer from
the state where the L0 layer is recorded/reproduced in the double-layered
medium will now be described. At this time, the concave lens 108 is
located at the optimum position at the substrate thickness of 0.1 mm of
the L0 layer. Even if it is intended to move the focal point to the L1
layer in this state, since there is a substrate thickness difference of
0.025 mm between the L1 layer and the L0 layer, the converging spot on
the disc is blurred. In this state, the characteristics are as shown by
an S-character curve 1202 in FIG. 12B as compared with an S-character
curve 1201 in FIG. 12A which is obtained when the focal point is
in-focused to the L1 layer and the focusing acquisition cannot be
performed, so that there is a risk of failure in the movement of the
focal point to the L1 layer. Therefore, the optical pickup is operated,
for example, as shown in steps 1301 to 1306 in FIG. 13. When a command to
move the focal point to the L1 layer is sent to the optical pickup from
the drive controller 809, the position of the concave lens 108 is
forcedly moved so that the second predetermined voltage V2 is outputted
from the detecting circuit 807 of the position detecting sensor 805 (as
described above) before the focusing acquisition is performed to the L1
layer. If the optical pickup is set into such a state, the good
converging spot is obtained in the L1 layer, the characteristics are as
shown in the S-character curve 1201 shown in FIG. 12A, and the focusing
acquisition operation can be stably started. Further, actually, since the
substrate thickness of the L1 layer also has a variation depending on the
radial direction position of the disc, there is a possibility of
fluctuation of the optimum position of the concave lens 108. For example,
the position of the concave lens 108 is finely adjusted in a manner
similar to the method described before in the operation in the L0 layer.
Information regarding the position of the concave lens 108 in the L1
layer obtained by the driving operation so far is stored into the drive
controller 809 together with the operation history.

[0043]When the focal point is again moved to the L1 layer, the obtained
information is immediately transferred to the optical pickup from the
drive controller 809. In this manner, the focal point can be stably moved
to the L1 layer. Since the optimum position information of the concave
lens 108 in the L0 layer and the L1 layer were obtained by the driving
operation so far, by referring to those information, the stable operation
can be executed even in the continuous focal point movement along in the
L0 layer→L1 layer→L0 layer. Although the convex lens 109 is
fixed and the concave lens 108 is set to be movable in the embodiment,
contrarily, it is also possible to fix the concave lens 108 and set the
convex lens 109 to be movable.

[0044]The case of the BD medium has been described above. A case of the
DVD medium and the CD medium will be described hereinbelow. As shown in
FIG. 1, the beam expander element 110 is arranged on a common optical
path between the red laser 119 having the laser wavelength of the band of
660 nm, the infrared laser 129 having the laser wavelength of the band of
780 nm, and the objective lens 113. Therefore, in the case of
recording/reproducing the DVD medium or the CD medium, the position of
the concave lens 108 is set to a position different from that in the case
of the BD medium. In the case of the DVD medium, since the objective lens
113 is designed as described with reference to FIG. 2B, the initial
position of the concave lens 108 is set so that the red parallel light
emitted from the collimator lens 124 enters the concave lens 108 and the
parallel light from the convex lens 109 is emitted. For example, when a
trial calculation is performed by using the expander element shown in
Table 1 at the wavelength of 660 nm, it is sufficient to set the concave
lens 108 to the position which is away from the convex lens 109 in the
optical axis direction by 2.08 mm.

[0045]On the other hand, in the case of the CD medium, since the objective
lens 113 is designed as described with reference to FIG. 2c, although the
infrared parallel light emitted from the collimator lens 124 enters the
concave lens 108, the initial position of the concave lens 108 is set so
that the predetermined designed divergent light 211 is emitted from the
convex lens 109. For example, the objective lens designed so that a
virtual light emitting point is located at the position which is away
from a principal plane of the objective lens 113 by 90 mm at the
wavelength of 780 nm is presumed. When a trial calculation is performed
by using such an objective lens and the expander element shown in Table
1, it is sufficient to set the concave lens 108 to the position which is
away from the convex lens 109 in the optical axis direction by 0.32 mm.

[0046]When the optical pickup is assembled, adjustment is made, for
example, in steps 1401 to 1408 shown in FIG. 14. First, in the case of
the DVD, a DVD reference disc manufactured so that the substrate
thickness is set to the same value of 0.6 mm as that of the DVD medium is
used, the interferometer, spot observing apparatus, or the like is used,
and the initial position of the concave lens 108 is adjusted so that the
converging spot by the objective lens 113 enters the optimum state. Or,
the optical pickup is set into the state where the focusing servo can be
performed and the initial position of the concave lens 108 is adjusted so
as to optimize the jitter value and the error rate value. In this state,
electrical adjustment is made on the circuit 807 side so that a third
predetermined voltage V3 is outputted from the detecting circuit 807 of
the position detecting sensor 805. Subsequently, a CD reference disc
accurately manufactured so that the substrate thickness is set to the
same value of 1.2 mm as that of the CD medium is used and the initial
position of the concave lens 108 is adjusted so that the converging spot
by the objective lens 113 is set into the optimum state or the jitter
value and the error rate value are optimized. In this state, electrical
adjustment is made on the circuit 807 side so that a fourth predetermined
voltage V4 is outputted from the circuit 807 of the position detecting
sensor 805.

[0047]The operation of the drive of the optical pickup adjusted as
mentioned above is, for example, as shown in steps 1501 to 1506 in FIG.
15 and will be explained hereinbelow also with reference to FIG. 8. When
the disc is loaded into the drive and it is determined that this disc is
the DVD medium (CD medium), the drive controller 809 refers to the
circuit 807 of the position detecting sensor 805 and the driver circuit
808 of the stepping motor 803. The stepping motor 803 is driven so that
the predetermined voltage V3 (V4) is outputted from the circuit 807,
thereby deciding the position of the concave lens 108. In this state, the
focusing acquisition is performed. When the focusing operation becomes
unstable during the operation, the optical axis direction position of the
concave lens 108 is finely adjusted. The information regarding the
position of the concave lens 108 is obtained by the driving operation so
far and stored into the drive controller 809 together with the operation
history. When the disc is ejected from the drive and the DVD medium (CD
medium) is again used, the obtained information is immediately
transferred to the optical pickup from the drive controller (not shown).
By constructing the system as mentioned above, such an effect that the
stable driving operation can be executed in a short time and the use
efficiency is improved can be obtained.

[0048]In the embodiment, in the state before the disc is loaded, the state
of the optical element for spherical aberration correction is preset so
that the converging spot on the disc is optimized at the substrate
thickness of 0.1 mm. This substrate thickness of 0.1 mm is a condition in
which it is presumed that it is a reference value of the substrate
thickness in the single-layered disc and the first layer of the
double-layered disc of the BDs and the use frequency is highest. Thus,
such a preset state can be set to a start point of the spherical
aberration correction and the spherical aberration correction control
after the disc was loaded can be most efficiently made.

[0049]As an embodiment 2, the optical pickup in which two objective lenses
of an objective lens for the BD and a DVD/CD-compatible objective lens
are mounted and which can cope with each medium of the BD, DVD, and CD
will be described. FIG. 16 shows the first example in the embodiment. In
this example, an objective lens 1601 for the BD and a DVD/CD compatible
objective lens 1603 are mounted on an axial sliding actuator 1602 of a
rotary type. The objective lens to be used is switched as shown by arrows
1604 in accordance with a kind of information recording medium 114. The
DVD/CD compatible objective lens 1603 is designed so as to optimize the
state of the converging spot on the recording surface of the information
recording medium 114 when the parallel light enters. For example, when a
trial calculation is performed by using the expander element shown in
Table 1 at the wavelength of 780 nm, it is sufficient to set the concave
lens 108 to the position which is away from the convex lens 109 in the
optical axis direction by 2.1 mm. Since an optical system up to the
objective lens 1601 for the BD or the DVD/CD compatible objective lens
1603 is common to that in FIG. 1 of the embodiment 1 and has already been
described in the embodiment 1, its explanation is omitted here.

[0050]FIG. 18 shows the second example in the embodiment. In the diagram,
an X axis, a Y axis, and a Z axis indicate a tangential direction, a
radial direction, and a surface oscillating direction of the information
recording medium, respectively. The upper stage shows an XY plan view and
the lower stage shows an XZ plan view. In this example, the objective
lens 1601 for the BD and the DVD/CD compatible objective lens 1603 are
arranged in parallel with the X axis and mounted on a lens holder 1801
and a fine translation driving in the Y-axis direction and the Z-axis
direction in the diagram and a fine rotational driving around the X axis
and the Y axis can be performed by an actuator (not shown) including a
driving coil 1802.

[0051]The divergent light emitted from the blue-violet laser 101 passes
through the polarization beam splitter 105, is converted into the
parallel light by the collimator lens 106 for the BD, reflected by a
return mirror 1804, transmitted through the beam expander element 110,
and reflected by a rising mirror 1803. After that, the light passes
through the quarter wave plate 112, is converged by the objective lens
1601 for the BD, and reaches the information recording surface of the
information recording medium 114 (in this case, the BD medium having one,
two, or more recording layers). A part of the divergent light emitted
from the blue-violet laser 101 is reflected by the polarization beam
splitter 105, is converged by the lens 115, and reaches the front monitor
116 for the BD, and a light emission amount of the blue-violet laser 101
is monitored. The reflection return light from the information recording
medium 114 passes through the objective lens 1601 for the BD and the
quarter wave plate 112, reflected by the rising mirror 1803, transmitted
through the beam expander element 110, and reflected by the return mirror
1804. After that, the light passes through the collimator lens 106, is
reflected by the polarization beam splitter 105, is converged by the
detecting lens 117, and reaches a detecting surface of the photodetector
118 for the BD.

[0052]After the divergent light emitted from the red laser 119 passes
through the synthetic prism 122, it is reflected by the half mirror 123.
Parallel light is irradiated from a collimator lens 1805. After that, the
resultant light is reflected by the rising mirror 1803, converged by the
DVD/CD compatible objective lens 1603, and reaches the information
recording surface of the information recording medium 114 (in this case,
the DVD medium having one or two recording layers). The reflection return
light from the information recording medium 114 passes through the DVD/CD
compatible objective lens 1603, is reflected by the rising mirror 1803,
and is transmitted through the collimator lens 1805 and the half mirror
123. The light is converged by the detecting lens 127 and reaches the
photodetecting surface of the photodetector 128 for the DVD/CD.

[0053]The divergent light emitted from the infrared laser 129 having the
laser wavelength of the band of 780 nm is reflected by the synthetic
prism 122 and the half mirror 123 and the parallel light is emitted from
the collimator lens 1805. After that, it is reflected by the rising
mirror 1803, is converged by the DVD/CD compatible objective lens 1603,
and reaches the information recording surface of the information
recording medium 114 (in this case, the CD medium). Since the optical
path until the reflection return light from the information recording
medium 114 reaches the photodetecting surface of the photodetector 128
for the DVD/CD is substantially the same as that of the DVD optical
system of the red laser 119, its description is omitted here.

[0054]FIG. 19 shows the third example in the embodiment. In the diagram,
the X axis, Y axis, and Z axis indicate the tangential direction, radial
direction, and surface oscillating direction of the information recording
medium, respectively. The upper stage shows an XY plan view and the lower
stage shows a YZ plan view. In this example, the objective lens 1601 for
the BD and the DVD/CD compatible objective lens 1603 are arranged in
parallel with the Y axis and mounted on a lens holder 1901 and a fine
translation driving in the Y-axis direction and the Z-axis direction in
the diagram and a fine rotational driving around the X axis and the Y
axis can be performed by an actuator (not shown) including a driving coil
1904. A rising mirror 1902 for the BD reflects the BD light entering from
the -X direction in the diagram and allows it to enter the objective lens
1601 for the BD. A rising mirror 1903 for the DVD/CD reflects the DVD/CD
light entering from the Y direction in the diagram and allows it to enter
the DVD/CD compatible objective lens 1603. Since the other optical path
is substantially the same as that in the second example, its description
is omitted here.

[0055]FIG. 20 shows the fourth example in the embodiment. In the diagram,
the X axis, Y axis, and Z axis indicate the tangential direction, radial
direction, and surface oscillating direction of the information recording
medium, respectively. A broken line section 2001 at the upper stage shows
the optical pickup for the DVD/CD on which the DVD/CD optical system has
been mounted. A broken line section 2002 at the lower stage shows the
optical pickup for the BD on which the BD optical system has been
mounted. Those optical pickups are enclosed in different pickup casings
(not shown).

[0056]Although the red laser 119 and the infrared laser 129 are separately
provided in FIGS. 16, 18, 19, and 20, a double-wavelength laser in which
those lasers are integrated can be used in order to simplify the optical
system. For example, an optical system in which the blue-violet laser 101
and the red laser 119 have been mounted without using the infrared laser
129 can be also used in accordance with the specification of the drive.

[0057]The examples of the optical pickups have been described in the
embodiments 1 and 2. An embodiment of an optical information recording
and reproducing device on which the foregoing optical pickup has been
mounted will now be described. FIG. 17 shows a schematic block diagram of
an information recording and reproducing device 1701 for executing
reproduction or recording/reproduction of information. Reference numeral
1702 denotes an optical pickup described in the embodiments 1 and 2. A
signal detected from the optical pickup 1702 is sent to a servo signal
generating circuit 1703 and an information signal reproducing circuit
1704 in a signal processing circuit. In the servo signal generating
circuit 1703, a focusing control signal, a tracking control signal, and a
spherical aberration detection signal suitable for an optical disk medium
1705 are formed from the signal detected by the optical pickup 1702. On
the basis of those signals, an ACT (not shown) in the optical pickup 1702
is driven by an ACT driving circuit 1706, thereby controlling the
position of an objective lens 1707. In the servo signal generating
circuit 1703, the spherical aberration detection signal is generated from
the optical pickup 1702. On the basis of this signal, a correcting lens
of a beam expander element (not shown) in the optical pickup 1702 is
driven by a spherical aberration correction driving circuit 1708. In the
information signal reproducing circuit 1704, an information signal
recorded on the optical disk 1705 is reproduced from the signal detected
from the optical pickup 1702. The information signal is outputted to an
information signal output terminal 1709. A part of the signals obtained
by the servo signal generating circuit 1703 and the information signal
reproducing circuit 1704 are sent to a system control circuit 1710. A
recording signal for laser driving is sent from the system control
circuit 1710 and a laser light source turn-on circuit 1711 is driven,
thereby controlling the light emission amount and recording the recording
signal onto the optical disk 1705 through the optical pickup 1702. An
access control circuit 1712 and a spindle motor driving circuit 1713 are
connected to the system control circuit 1710 and radial direction
position control of the optical pickup 1702 and rotation control of a
spindle motor 1714 of the optical disk 1705 are made, respectively. In
the case where the user makes control by a personal computer, a recorder
for AV, or the like, he gives an instruction to a user input processing
circuit 1715 from a user input device 1718 such as keyboard, touch panel,
jog dial, or the like, thereby controlling the information recording and
reproducing device 1701. At this time, a processing state or the like of
the information recording and reproducing device 1701 is processed by a
display processing circuit 1716 and displayed by a display device 1717
such as liquid crystal panel, CRT, or the like.

[0058]While we have shown and described several embodiments in accordance
with our invention, it should be understood that disclosed embodiments
are susceptible of changes and modifications without departing from the
scope of the invention. Therefore, we do not intend to be bound by the
details shown and described herein but intend to cover all such changes
and modifications within the ambit of the appended claims.